Beryllium-copper alloys having a variety of compositions and presenting a range of properties, both mechanical and electrical, are known. Such alloys may contain beryllium in the range of about 0.1% to about 3% to confer age hardenability through a precipitation hardening heat treatment and may contain small amounts of other alloying ingredients such as cobalt, nickel, silver, etc. for special purposes. The alloys in strip form are useful for the production of connectors, switch parts, relays and many other parts amenable to production in progressive dies. In rod, bar, tube and plate form the alloys find use in machined connectors, welding electrodes, injection molding tooling and similar applications. As uses of the alloys have progressed, a demand has arisen for stronger alloys which would still retain significant ductility, electrical conductivity, formability and other desirable properties. For example, the strength of the alloys can be increased by application of cold work in amounts up to possibly 37%, e.g., 21%, after precipitation hardening, but such a practice reduces the ductility and formability of the material and, in addition, electrical conductivity is also degraded. On the other hand, increases in conductivity may be achieved by substantial overaging, but at the expense of strength.
Heat treatment of the alloys usually involves a solution annealing treatment to insure solid solution of the alloying elements added for strengthening, and a precipitation-hardening (aging) heat treatment. Solution annealing of the alloys is conducted commercially at a temperature in the range of about 1325.degree. F. to about 1650.degree. F. for short periods, e.g., about 5 minutes. A quench, e.g., a water quench, is employed after solution treating to retain alloying elements in solution. Aging is usually conducted in the temperature range of about 450.degree. F. to about 925.degree. F. for periods of up to about 4 hours.
The invention is directed to a thermomechanical process for providing, in certain beryllium-copper alloys, improved strength, ductility and formability as compared to the properties attainable by prior procedures, without degradation of conductivity.